WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 AM AST (0900 UTC), the center of Tropical Depression
Seventeen was located near latitude 31.1 North, longitude 39.9 West.
The depression is moving toward the north near 3 mph (6 km/h), and
this motion is expected to continue today. A turn to the east and
east-southeast is expected to occur tonight and Tuesday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some strengthening is forecast, and the depression is expected to
become a tropical storm later today or tonight.

The estimated minimum central pressure is 1008 mb (29.77 inches).

HAZARDS AFFECTING LAND
----------------------
None.

NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Cangialosi

Last edited by ccstorms on Mon Oct 16, 2017 4:35 am; edited 3 times in total

The well-defined low pressure system over the eastern Atlantic
several hundred miles southwest of the Azores has maintained an
area of deep convection near and to the east of the center for the
past several hours. Therefore, the system now meets the criteria
for a tropical depression. The initial intensity is estimated to be
30 kt based on ASCAT data from around 0000 UTC and a 2.0/30 kt
Dvorak classification from TAFB.

The depression is moving slowly northward at 3 kt, and a continued
slow north to north-northeast motion is expected today. A turn to
the east and then southeast is forecast to begin tonight and
continue through Wednesday while the cyclone is steered by the flow
on the east side of a subtropical ridge. Thereafter, a mid- to
upper-level trough is expected to approach the depression, and that
should cause the system to move a little faster to the east and
east-northeast. The NHC track forecast lies near the middle of the
guidance envelope, in agreement with various consensus aids, and
keeps the system far from any land areas.

The depression is currently over marginally warm 27 deg C SSTs and
in an environment of moderate to strong westerly shear. The
models suggest that the shear will likely let up a little during the
next couple of days, which could allow the depression to gradually
strengthen while it remains over relatively warm waters. After that
time, the shear could increase again, but the amount of shear
depends on the exact track of the tropical cyclone. There is a fair
amount of spread in the models at the longer range with the regional
models (HWRF, HMON, and COAMPS-TC) bringing the system to hurricane
strength while the statistical SHIPS and LGEM models show a much
weaker system. The NHC intensity forecast leans toward the more
conservative side of the guidance for now, but it should be noted
that confidence in the intensity forecast is low.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 AM AST (1500 UTC), the center of Tropical Storm Ophelia was
located near latitude 31.4 North, longitude 39.9 West. Ophelia is
moving toward the north-northeast near 5 mph (7 km/h), and a turn
toward the northeast is expected later today. A motion toward
the east-northeast and east is forecast to occur later tonight,
followed by a turn toward the east-southeast on Tuesday.

Maximum sustained winds have increased to near 40 mph (65 km/h) with
higher gusts. Some strengthening is forecast during the next 48
hours.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.

The convective pattern of the small cyclone has continued to improve
since the previous advisory, with some thunderstorm activity having
developed near or over the center, along with an increase in curved
banding features in the eastern semicircle. The Dvorak intensity
estimate at 1200Z from TAFB was T2.0/30 kt, but given the
aforementioned improvement in the curved-band structure since that
time, the initial intensity is increased to 35 kt. This makes
Ophelia the fifteenth named storm of the 2017 Atlantic hurricane
season.

The initial motion estimate is 030/04 kt. The steering flow
surrounding Ophelia is expected to continue to be weak for the next
day or so while the cyclone remains entangled with a weak
upper-level low located just to its north and northwest. As a
result, only a slow drift toward the northeast and and east is
forecast. By 36 h, increased mid-level ridging to the northwest of
Ophelia should induce a motion toward the east-southeast and
southeast through 72 h, after which a broad mid-latitude trough is
expected to gradually accelerate the cyclone toward the northeast at
a forward speed of near 10 kt. The official forecast remains down
the middle of the guidance envelope, in close agreement with the
previous forecast track, and the HCCA and TVCX consensus models.
Ophelia should remain far away from land for the next 5 days.

Although Ophelia is forecast to remain over marginally warm SSTs of
26.5-27 deg C, much colder-than-normal temperatures aloft should
offset the relatively cool ocean temperatures and produce sufficient
instability to generate moderate to strong convection for the next
120 h. The GFS-based SHIPS model is currently assessing 25 kt of
westerly vertical wind shear, which obviously isn't occuring based
on the recent development of anticyclonic outflow over the low-level
center and across most of Ophelia's circulation. In contrast, the
UW-CIMSS shear analyses indicate lower shear values near 15 kt.
However, both shear assessments are likely too high given the large
domains that they use to calculate environmental wind shear. Based
on recent trends noted in water vapor imagery showing the shear
decreasing, along with the overall favorable upper-level wind fields
forecast by the GFS and ECMWF, especially after 36 hours, slow but
steady strengthening is expected for the next 5 days, with only
occasional intrusions of dry mid-level air being the primary
inhibiting factor to the intensification process. The official
intensity forecast is close to the NOAA HCCA consensus model, is
about midway between the more aggressive IVCN consensus model that
makes Ophelia a hurricane in about 72 h, and the more conservative
statistical SHIPS and LGEM models. However, even the SHIPS and LGEM
models have increased their peak intensity forecasts by at least 15
kt since the previous advisory.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Ophelia was
located near latitude 31.5 North, longitude 39.6 West. Ophelia is
moving toward the northeast near 3 mph (6 km/h). A slow motion
toward the east-northeast and east is forecast to occur later
tonight, followed by a turn toward the southeast on Tuesday.

Maximum sustained winds have increased to near 45 mph (75 km/h) with
higher gusts. Additional strengthening is forecast during the next
48 hours.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 AM AST (0900 UTC), the center of Tropical Storm Ophelia was
located near latitude 31.9 North, longitude 38.8 West. Ophelia is
moving toward the southeast near 3 mph (6 km/h), and this general
motion is expected to continue during the next day or two.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts.
Gradual strengthening is forecast, and Ophelia is expected to become
a hurricane by Wednesday.

Tropical-storm-force winds extend outward up to 105 miles (165 km)
from the center.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 AM AST (1500 UTC), the center of Tropical Storm Ophelia was
located near latitude 31.5 North, longitude 38.3 West. Ophelia is
moving toward the southeast near 5 mph (7 km/h), and this general
motion is expected to continue during the next day or two.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts.
Gradual strengthening is forecast during the next 48 hours, and
Ophelia is expected to become a hurricane by Thursday.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Ophelia was
located near latitude 31.1 North, longitude 38.0 West. Ophelia is
moving toward the southeast near 6 mph (9 km/h) and this general
motion is expected to continue during the next day or two.

Maximum sustained winds have increased to near 60 mph (95 km/h) with
higher gusts. Additional strengthening is forecast during the next
48 hours, and Ophelia is expected to become a hurricane by Thursday.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.

WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 AM AST (0900 UTC), the center of Tropical Storm Ophelia was
located near latitude 30.2 North, longitude 37.0 West. Ophelia is
moving toward the southeast near 6 mph (9 km/h). A southeastward
to east-southeastward motion with some reduction in forward speed
is expected through Thursday, followed by a turn toward the
east-northeast by Thursday night or Friday.

Maximum sustained winds have increased to near 65 mph (100 km/h)
with higher gusts. Additional strengthening is forecast during the
next 48 hours, and Ophelia is expected to become a hurricane
Wednesday night or Thursday.

Tropical-storm-force winds extend outward up to 60 miles (95 km)
from the center.

Ophelia has become better organized during the past several hours,
with convective banding now wrapping almost all of the way around
the center. Satellite intensity estimates from TAFB and SAB have
increased to 55 kt and 65 kt, respectively, and several recent
microwave-based intensity estimates are in the 55-65 kt range.
Based on this, the initial intensity is increased to a possibly
conservative 55 kt.

The initial motion is now 125/5. Ophelia should continue to move
southeastward or east-southeastward during the next 12-24 hours with
a decrease in forward speed while it remains embedded within a mid-
to upper-level trough to the south of the mid-latitude westerlies.
After that, the cyclone is forecast to turn northeastward and
accelerate by day 3 ahead of a deepening mid-latitude trough over
the north-central Atlantic. The latest track guidance is in good
agreement with this scenario. However, there has been a significant
northward shift in the 120 h forecasts since the last advisory. The
new official forecast track is similar to the previous track through
72 h, and then is adjusted northward at the 96 and 120 h points. It
should be noted, though, that the 120 h point is to the south of the
consensus and large-scale models, and additional northward
adjustments may be required later.

The cyclone is expected to be within a low shear environment and
over marginally warm sea surface temperatures during the next 2 to 3
days. These conditions favor strengthening and the NHC forecast
now calls for Ophelia to become a hurricane in about 24 hours.
Extratropical transition is likely to start around day 4 and be
complete by day 5, with the associated baroclinic dynamics expected
to keep Ophelia a strong cyclone over the northeastern Atlantic.